How do I calculate the molecular mass of a compound?
Answer
The molecular mass of a compound is equal to the sum of the masses of its total atoms in its formula.
For example, water is H20 and contains 2 atoms of Hydrogen and 1 atom of Oxygen. From the atomic weights on the periodic table, H=1 and O=16, so the molecular mass = 2x1 + 16 = 18 amu [atomic mass units]. 1 mole of water will have a mass of 18 grams from Avogadro's Law.
Sucrose [Sugar] has a formula of C6H12O6 and has 6xC + 12xH + 6xO = 6x12 + 12x1 + 6x16 = 72 + 12 + 96 = 180 amu. 1 mole of sucrose will have a mass of 180 g.
Sulfuric acid is H2SO4 and has 2xH + 1xS + 4xO = 2x1 + 1x32 + 4x16 = 2 + 32 + 64 = 98 amu. Thus, 1 mol sulfuric acid = 98 g.